JPH0145123Y2 - - Google Patents

Description

[Detailed explanation of the idea]

[Technical Field of the Invention] This invention relates to a signal synthesizer, and particularly to a signal synthesizer using a λ/4 impedance transformer. [Technical background of the invention and its problems] In recent years, in television broadcasting equipment such as VHF or UHF, outputs of multiple power amplifiers are combined in parallel to achieve high power output. A signal synthesizer using a λ/4 impedance transformer is used as a signal synthesizer for synthesizing the outputs of the power amplifiers. λ indicates the wavelength of the transmission signal. This combiner takes the output impedance of the power amplifier as Z ₁ , the output load impedance as Z ₂ , and the number of combinations as N
Then, from the matching condition, the characteristic impedance W _T of the λ/4 impedance transformer is W _T =√Z ₁ /N×Z ₂ [Ω] …(1), and since Z ₁ = Z ₂ in general, Z If ₁ = Z ₂ = Z ₀ , then W _T = Z ₀ /√N [Ω] ...(2), and with this characteristic impedance W _T , any combination can be performed using a transmission line of λ/4 length. . As a signal synthesizer using such a λ/4 impedance transformer, the one shown in FIG. 1 is in practical use. As shown, this synthesizer is
It is composed of a coaxial feeder 1, and the figure shows two combinations, 41 and 42 are input terminals, 31 is a combination output terminal, 2 is an outer conductor, 4 is an inner conductor,
The coaxial feeder 1 has a length of λ/4 from the composite end 21. By the way, as is well known, the characteristic impedance W of the coaxial feeder 1 is determined by W=138/√εlog ₁₀ D/d [Ω] (3). That is, it is determined by the dielectric constant ε of the gap between the outer conductor 2 and the inner conductor 4 and the ratio between the inner diameter D of the outer conductor 2 and the outer diameter d of the inner conductor 4. Note that since the gap between the outer conductor 2 and the inner conductor 4 is generally filled with air, ε=1, and any characteristic impedance can be obtained by selecting D/d. In this signal synthesizer using a coaxial feeder, its characteristic impedance W must match the characteristic impedance W _T in equation (1) above, but D, d, or ε must be selected in accordance with the characteristic impedance W _T. However, selecting the characteristic impedance W has become complicated. [Object of the invention] The present invention has been made in view of the above points, and an object thereof is to obtain a signal synthesizer using a coaxial feeder that can easily set the characteristic impedance. [Summary of the invention] In the present invention, a dielectric material having a dielectric constant corresponding to the signal composite number is placed in the gap between the outer conductor and the inner conductor of the coaxial feeder, which has a characteristic impedance equal to the circuit impedance to which the connection is made. The dielectric material is inserted with a length that is one-fourth of that of the dielectric material, and the characteristic impedance is set by this dielectric material. [Embodiment of the invention] An embodiment of the invention will be described below with reference to FIG. 2. Note that the same reference numerals are used for parts corresponding to those in FIG. In the figure, 1 is a coaxial feeder, 41 and 42 are input terminals, and 31 is a composite output terminal, and the characteristic impedance W of this coaxial feeder 1 is the output terminal 31.
The circuit impedance such as the load impedance connected to the circuit is made equal to the circuit impedance _Z0 . In the television transmitter, the load impedance Z ₀ is 50 [Ω], and the characteristic impedance W of the coaxial feeder 1 is also 50 [Ω]. Several types of coaxial feeders 1 having a characteristic impedance W of 50 [Ω] are currently in use as shown in the table below, and one can be selected from these.

[Effect of idea]

As described above, according to the present invention, by selecting a dielectric to be inserted into a coaxial feeder having a characteristic impedance W equal to the circuit impedance to be connected, it is possible to easily set the impedance to the circuit impedance.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a conventional signal synthesis device, FIG. 2 is a perspective view showing an embodiment of the signal synthesis device according to the present invention, and FIG. 3 is a perspective view showing another embodiment of the invention. FIG. 4 is a perspective view showing a modification of the dielectric shown in FIGS. 2 and 3. FIG. 1... Coaxial feeder, 2... Outer conductor, 4... Inner conductor, 6... Dielectric, 31... Combined output terminal, 4
1, 42, 51, 52, 53, 54...input terminals.

Claims (1)

[Claims for Utility Model Registration] 1. A coaxial feeder that is provided with a plurality of input terminals at one end, a composite output terminal at the other end, and has a characteristic impedance equal to the impedance of the circuit to which it is connected, and the composite end of this coaxial feeder and its composite A signal combiner, the signal combiner comprising: a dielectric material inserted between an outer conductor and an inner conductor of the coaxial feeder between the end and a position one-fourth of the transmission signal wavelength, and having a dielectric constant corresponding to the number of signal combinations. 2. The signal synthesizer according to claim 1, wherein the dielectric constant of the dielectric is within the range of -10% to +10% of a value equal to the number of signal combinations.